Dimmer switches, i.e., wall-mounted light switches that include a dimmer, have become increasingly popular, especially for applications where it is desired to control precisely the level of light intensity in a particular room. Some known dimmer switches employ a variable resistor that is manipulated by hand to control the switching of a triac, which in turn varies the voltage input to the lamp(s) to be dimmed. Such manually-operated, variable resistor dimmer switches have a number of known limitations. There exist touch actuator controls that address at least some of these limitations.
One such touch actuator control cycles repetitively through a range of intensities from dim to bright in response to extended touch inputs. A memory function is provided such that, when the touch input is removed, the cycle will be stopped and the level of light intensity at that point in the cycle will be stored in a memory. A subsequent short touch input will turn the light off, and a further short touch input will turn the light on at the intensity level stored in the memory. While this type of switch is an improvement over manually-operated variable resistor dimmer switches, it requires the user to go through the cycle of intensity levels in order to arrive at a desired intensity level. In addition, it still lacks the ability to return to a desired intensity level after having been set to full light output. A user must go through the cycle again until he or she finds the light intensity level desired. Moreover, this type of switch typically has no ability to perform certain aesthetic effects such as a gradual fade from one light intensity level to another.
U.S. Pat. No. 5,248,919 (“the 919 patent”) discloses a lighting control that may include user-actuatable intensity selecting means for selecting a desired intensity level between a minimum intensity level and a maximum intensity level, and control switch means for generating control signals representative of preselected states and intensity levels in response to an input from a user. The disclosure of the 919 patent is incorporated herein in its entirety.
The 919 patent further discloses control means for causing at least one lamp to fade: a) from an off state to the desired intensity level, at a first fade rate, when the input from a user causes a switch closure; b) from any intensity level to the maximum intensity level, at a second fade rate, when the input from a user causes two switch closures of transitory duration in rapid succession; c) from the desired intensity level to an off state, at a third fade rate, when the input from a user causes a single switch closure of a transitory duration; and d) from the desired intensity level to an off state, at a fourth fade rate, when the input from a user causes a single switch closure of more than a transitory duration. The control means may cause the lamp to fade from a first intensity level to a second intensity level at a fifth fade rate when the intensity selecting means is actuated for a period of more than transitory duration.
FIG. 1 depicts a prior art wall control 10 as described in the 919 patent. As shown, wall control 10 comprises a cover plate 12, an intensity selection actuator 14 for selecting a desired level of light intensity of a lamp or lamps controlled by the device, and a control switch actuator 16. Actuation of the upper portion 14a of actuator 14 increases or raises the light intensity level, while actuation of lower portion 14b of actuator 14 decreases or lowers the light intensity level. Wall control 10 may also include an intensity level indicator in the form of a plurality of light sources 18, which may be light-emitting diodes (LEDS), for example. By illuminating a selected one of light sources 18, the position of the illuminated light source within the array may provide a visual indication of the light intensity level of the lamp or lamps being controlled.
Example fade rates and fade rate profiles illustrated in the 919 patent are reproduced as FIGS. 2A–2D hereof. FIG. 2B illustrates a first fade rate, at which a lamp fades up from an off state to a desired intensity level. The first fade rate from “off” to a desired intensity level is labeled with reference numeral 40. FIG. 2B illustrates the fade rate in terms of a graph of normalized light intensity level, from “off” to 100%, vs. time, given in seconds. As shown, fade rate 40 may fade from “off” to 100% in about 3.5 seconds, i.e., at the rate of about +30% per second. This fade rate is used when the lighting control device 10 of the invention receives as a user input a single tap of the control switch actuator 16 and the lamp under control was previously off. This fade rate may, but need not, also be used when a user selects a desired intensity level by actuating intensity selection actuator 14. Thus, the lamp 20 will fade up from one intensity level to another at fade rate 40 when upper portion 14a of actuator 14 is actuated by the user.
Similarly, FIG. 2C illustrates a fade rate 42 at which lamp 20 will fade down from one intensity level to another when actuator 16 is tapped when the lamp under control is already on or lower portion 14b of actuator 14 is actuated by the user. Fade rate 42 is illustrated as being the same as fade rate 40, but with opposite sign, and fades down from 100% to “off” in about 3.5 seconds, for a fade rate of about 30% per second. However, it will be understood that the precise fade rates are not crucial, and that fade rates 40 and 42 can be different.
FIG. 2A illustrates a second fade rate 44 at which lamp 20 fades up to 100% when the lighting control device 10 receives as a user input two quick taps in succession on control switch actuator 16. As noted above, two quick taps on actuator 16 cause lamp 20 to fade from its then-current light intensity level to 100%, or full on. Fade rate 44 may be substantially faster than first fade rate 40, but not so fast as to be substantially instantaneous. An example fade rate 44 is about +66% per second. If desired, the fade rate 44 can be initiated after a short time delay, such as 0.3 seconds, or can, in that interval, be preceded by a slower fade rate 46.
A “hold” input at actuator 16 causes lamp 20 to fade from its then-current intensity level to off at a third fade rate 48, as shown in FIG. 2D. Fade rate 48 may be substantially slower than any of the previously illustrated fade rates. Fade rate 48 also may not be constant, but may vary depending upon the then-current intensity level of lamp 20. However, the fade rate may be such that the lamp 20 will fade from its then-current intensity level to off in approximately the same amount of time for all initial intensity levels. For example, if lamp 20 is desired to fade to off in about ten seconds (to give the user time to cross a room before the lights are extinguished, for example), a fade rate of about 10% per second may be used if the then-current intensity level of the lamp 20 is 100%.
On the other hand, if the then-current intensity level of lamp 20 is only 35%, the fade rate may be only 3.5% per second, so that the lamp 20 will not reach full off until the desired ten seconds. In addition, if desired, a slightly faster fade rate 50 may be used in the initial half-second or so of fadeout, in order to give the user immediate feedback to confirm that the fadeout has been initiated. A suitable fade rate 50 may be on the order of 33% per second. A similarly more rapid fade rate 52 may also be used near the very end of the fadeout, so that the lamp 20 be quickly extinguished after fading to a low level. Thus, after about ten seconds of fadeout, at a relatively slow rate, the lamp 20 will fade the rest of the way to off in about one more second. If the fast initial and final fade rates are used, then the intervening fade rate must be slowed down to achieve the same fade time.
As illustrated in FIG. 2D, however, with lower initial intensity levels, the intervening fade rate may be zero (constant light output), and with even lower initial intensity levels, the lamp may fade off during the initial fast fade. Thus, at low light intensities (e.g., less than about 20%), the control means tends to turn off the lamp before the long fade off is activated (i.e., before detection that the single switch closure is of more than a transitory duration). It would be desirable if such light controls were capable of activating a long fade off from any light intensity.